1. Technical Field
This disclosure relates to a method and system for physiologic vibration quantification and, more particularly, to a method and system for quantifying postural sway to determine postural instability or imbalance.
2. Description of the Related Art
Falls represent a serious medical problem in the United States. As one example, consider that some 250,000 individuals fall each year fracturing their hip. This generally results in total hip arthroplasty or hip replacement surgery at a significant cost. Health care costs in this area range in the billions of dollars per year in the United States alone. Further, the morbidity associated with hip fractures is extensive. Half of all individual who undergo total hip arthroplasty will not achieve their previous level of motility and will require assistance to walk. Moreover, for patients over 70, more than one-half will die within 12 months of a hip fracture due to complications associated with the surgery or extended bed rest following surgery. Other consequences as a result of falling include lost wages, lost productivity, upper extremity injuries, head injuries, fear of falling leading to decreased physical activity, etc.
The primary cause of falling is loss of balance, and the inability to re-achieve balance once it is lost, concepts referred to as postural instability or imbalance. Postural instability is closely tied to the status of the neuro-muscular system, though a thorough understanding of the factors that lead to, or detract from, postural stability has yet to be established.
While all of the physiologic factors ensuring postural stability are not necessarily known, it is still possible to quantify postural stability. A number of methodology and measures have been proposed to characterize postural sway. The majority of the approaches rely on. xe2x80x9cforce platesxe2x80x9d or pressure sensitive detectors to identify the redistribution of body weight at the feet, though alternative approaches, (e.g. upper body position detection) have been proposed. These devices are sometimes utilized with the patient standing quietly on a rigid surface, but also, active perturbation of the patient can be imposed and recovery from the perturbation evaluated.
Analysis of the postural sway data can be done in the time domain, for example, evaluation of peakxe2x80x94peak sway magnitude. Analysis can also be done in the frequency domain which includes sophisticated stabilogram-diffusion analysis, as well as spectral analysis procedures. Frequency domain analysis approaches have led to the observation that the decrease in postural stability in the elderly is associated with a change in the slope of the spectral content of the postural sway.
However, such frequency spectra can be difficult to interpret as individuals can rely on a variety of strategies to maintain postural stability. For example, young adults are quite capable of standing quietly with little postural sway, though some young adults permit themselves to undergo extensive body sway excursion without fear of falling due to their superior postural stability. Spectral sway analysis procedures which do not account for such phenomena can lead to an incorrect diagnosis of sway condition.
Accordingly, a method and system are needed for quantifying postural sway to determine postural instability or imbalance of individuals.
The present disclosure describes a method and system for accurately and reproducibly characterizing postural sway to determine postural instability or imbalance. The method entails recording postural stability while the individual is standing on a non-rigidly supported platform of a postural quantifying system of the present disclosure.
The method of the present disclosure provides two distinct features. First, the intrinsic instability of the non-rigid platform forces the individuals to control their posture in dynamic, rather than static situation, so that a more accurate determination of postural stability is obtained. Second, By utilizing a moving platform, position, velocity or acceleration sensors can be used in place of force sensors as used in prior art systems, thus allowing less expensive system construction.
In particular, the present disclosure provides a non-invasive method for evaluating a musculoskeletal system of a patient including the steps of: providing a vibration measurement device in proximity to a non-rigidly supported platform; measuring a vibrational response of the patient""s musculoskeletal system using the vibration measurement device after the patient rests on the non-rigidly supported platform; performing a frequency decomposition of the vibrational response to quantify the vibrational response into specific vibrational spectra; and analyzing the vibrational spectra to evaluate at least postural stability.
The present disclosure also provides a non-invasive physiologic vibration quantification system for evaluating a musculoskeletal system of a patient undergoing controlled mechanical perturbation. The system includes vibration means for externally transferring vibrations to the musculoskeletal system and including a vibration measurement device for measuring a response by the musculoskeletal system in accordance with the vibrations transferred by the vibration means and for forming signals representative of the musculoskeletal system response; and an analyzer coupled to the vibration measurement device for receiving the signals from the vibration measurement device and developing a frequency spectrum associated with the signals. The frequency spectrum provides vibrational quantification of the musculoskeletal system for evaluating at least postural stability.